Electrolytic method to make alkali alcoholates using ceramic ion conducting solid membranes

ABSTRACT

Disclosed are processes of making solutions of metal alcoholates in their corresponding alcohols using an electrolytic process. In one embodiment, sodium methylate in methanol is made from methanol and sodium hydroxide solution. The sodium hydroxide solution is placed in the anolyte compartment and the methanol is placed in the catholyte compartment, and the two compartments are separated by a ceramic membrane that selectively transports sodium under the influence of current. In preferred embodiments, the process is cost-effective and not environmentally harmful.

RELATED APPLICATION INFORMATION

This application claims priority under 35 U.S.C. §119(e) to U.S.Provisional Patent Application No. 60/528,612, filed Dec. 11, 2003; toU.S. Utility patent application Ser. No. 11/010,822, to Shekar Balagopaland Vinod K. Malhotra, entitled “Electrolytic Method to Make AlkaliAlcoholates using Ceramic Ion Conducting Solid Membranes,” filed Dec.13, 2004; and to PCT Patent Application No.: PCT/US2004/041587, toShekar Balagopal and Vinod K. Malhotra, entitled “Electrolytic Method toMake Alkali Alcoholates using Ceramic Ion Conducting Solid Membranes,”filed Dec. 13, 2004. Each of these applications is incorporated hereinin its entirety by this reference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

This invention relates to electrochemical production of alkalialcoholates from alkali metal salt solutions and alcohol by using an ionconducting ceramic solid electrolyte or membrane based electrochemicalcell. In some specific embodiments, the process includes the use ofsodium-ion conducting ceramic membranes.

2. Description of the Related Art

Electrolytic systems have been proposed for use in producing alkalialcoholates from salt solutions. In these, various materials have beensuggested for use as an ion-conducting membrane positioned between theanolyte and catholyte chambers for transportation of ions there through.Such materials include ceramic materials alone, polymeric materials, andcombinations of ceramic and polymeric materials.

A known advantage of polymeric materials as electrolytes in theelectrolysis of salt solutions is their high conductivity and highresistance to acidic and caustic environments resulting from theelectrolytic process. A known disadvantage of polymers, however, istheir low selectivity for ionic species: that is, along with the desiredalkali metal ions, polymers may transport unwanted protons and cationsand may also cause the electroosmotic transport of water, the result ofwhich is-an inefficient operation of the electrolytic cell.

In one specific example, there are two primary methods of making sodiummethylate, also called sodium methoxide, that are in current use. Thefirst is a sodium-based process in which sodium metal is reacted withmethanol to produce sodium methylate. This method uses sodium metal as araw material, which may be expensive and which may react violently withlower alcohols, thus rendering the process difficult to control. Sodiummetal also reacts violently with water requiring elaborate and expensiveequipments and systems for storage, handling, and delivery of sodiummetal.

In a second process, sodium methylate is made from a sodium amalgamproduced from the chlor-alkali electrolysis in a mercury cell byreacting amalgam with alcohol. The drawback of this process is it canresult in the contamination of the product and the environment withmercury, a well known carcinogen. For this reason, use of sodiummethylate produced by this method is, in many cases, unattractive foragriculture, pharmaceuticals, and bio-diesel applications.

Thus, it would be an improvement in the art to provide a novel processand apparatus for the electrochemical production of alkali alcoholatesfrom alkali metal salt solutions and alcohol using an ion-conductingceramic solid electrolyte membrane. Such methods and apparatus areprovided herein.

SUMMARY OF THE INVENTION

In view of the known methods, a method of making alkali alcoholates suchas, in one example, sodium methylate, that may be simple, safe,environmentally benign, and cost-effective, preferably one which is alsoenvironmentally responsible, is needed.

In accordance with the present invention, there is provided herein amethod of making alkali alcoholates, including, in one specificembodiment, sodium methylate. The method comprises feeding an alcoholsuch as methanol, into a catholyte compartment of an electrolytic cell,feeding an alkali metal salt solution such as sodium hydroxide, into ananolyte compartment of the cell, and applying potential across the cell.The anolyte compartment and the catholyte compartment of the cell areseparated by a ceramic membrane that, upon application of the electricpotential across the cell, selectively transports the alkali metalcations, including in some embodiments, sodium cations, from the anolytecompartment to the catholyte compartment. In some specific embodiments,the membrane is substantially impermeable to water, operates at a highcurrent density, and/or operates at a low voltage. The metal cations,following their transport across the membrane, react with the alcohol toform a metal alcoholate, such as, in some embodiments, sodium methylatein methanol, in the catholyte compartment of the cell. In the citedexample, sodium methylate is formed, as discussed in greater detailbelow.

In accordance with one embodiment of the methods of the presentinvention, there is provided a method for producing sodium methylatesolution. The method comprises feeding a catholyte solution comprisingmethanol into a catholyte compartment of an electrolytic cell, feedingan anolyte solution comprising one or more sodium salts in aqueoussolution into an anolyte compartment of the cell, and applying anelectric potential across the cell, whereby the sodium ions migrateacross the ceramic membrane and then react with the methanol in thecatholyte compartment of the cell to form sodium methylate. In specificembodiments, the anolyte compartment and the catholyte compartment areseparated by a ceramic membrane that, upon application of the electricpotential across the cell, selectively transports sodium cations fromthe anolyte compartment to the catholyte compartment. The ceramicmembrane is substantially impermeable to water and/or does not generallysuffer degraded performance when in contact with water.

Thus, in association with this method, an electrolytic cell forproducing sodium methylate solution is further provided within the scopeof the present invention. The cell comprises a catholyte compartmentcontaining a cathode and a solution comprising methanol or a dilutesolution of sodium methylate in methanol, an anolyte compartmentcontaining an anode and a solution comprising one or more sodium basedsalts; and a sodium-selective ceramic membrane separating the anolytecompartment and the catholyte compartment that selectively permits theflow of sodium cations from the anolyte compartment to the catholytecompartment upon application of a voltage across the cell. Certainembodiments have one or more of the following features: the membrane issubstantially impermeable to water; the membrane maintains a constantcurrent density for at least during 6 hours of the operation, preferablyfor the entire duration of the operation; and/or the cell operates at acurrent density of at least about 100 mA/cm².

The specific embodiments above may be adapted to other alkali metalcations and other alcohols, for the full scope of the inventiondisclosed herein, as will be readily apparent to those skilled in theart.

BRIEF DESCRIPTION OF THE DRAWING

FIG. 1 is a schematic representation of an electrolytic cell accordingto one specific embodiment.

FIG. 2 is a schematic representation of an electrolytic cell with a flatplate sodium ion conducting membrane as is used to make sodium methoxideaccording to another embodiment. Also shown are the half-cell reactionsfor producing sodium methoxide by the electrochemical process using asodium-selective ceramic membrane based electrolytic cell.

FIG. 3 is a graph illustrating the performance of ceramic membranescomprising NaSICON materials under similar operating conditions.

FIG. 4 is a graph illustrating the effect of temperature and sodiummethylate concentration on resistance of sodium methylate solution.

FIG. 5 illustrates the effect of anolyte and catholyte recycling flowrates on the over-all voltage of a sodium methylate-producing cell.

FIG. 6 illustrates the changes in voltage and concentration of sodiummethylate solution with time of a sodium methylate producing celloperating at constant current density.

FIG. 7 is a plot of the voltage of a sodium methylate producing cell atdifferent current densities.

FIG. 8 is a plot of the voltage, temperatures of anolyte and catholytesolutions, as a function of testing time of a sodium methylate producingcell.

FIG. 9 is an open cell test with nitrogen bubbled into the catholytechamber of the cell containing sodium methoxide.

FIG. 10 is a plot of estimated cell voltage versus concentration ofsodium methylate solution.

FIG. 11 is a plot of changes in cell voltage and sodium methylateconcentration of catholyte as a function of testing time using purecaustic solution as anolyte.

FIG. 12 is a plot of changes in cell voltage and sodium methylateconcentration of catholyte as a function of testing time using impurecaustic solution as anolyte.

FIG. 13 is a plot of changes in cell voltage and sodium methylateconcentration of catholyte as a function of testing time using impurecaustic solution as anolyte.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

The following description illustrates preferred embodiments of thepresent invention in detail. Those of skill in the art will recognizethat there are variations and modifications of the embodiments describedherein that are encompassed by the scope of the invention. Accordingly,the description of preferred embodiments should not be deemed to limitthe scope of the invention.

Disclosed herein are processes for the production of non-aqueous alkalialcoholates by electrolysis of an aqueous alkali metal salt solution. Inspecific embodiments, the process includes the use of sodium ionconducting ceramic membranes. In one embodiment, the method is anelectrolytic process to make sodium methylate in methanol from methanoland sodium hydroxide solution or from a dilute solution of sodiummethylate in methanol and sodium hydroxide solution. The processdescribed herein may also be used to make other alkali alcoholates inthe corresponding alcohol from alcohol and aqueous alkali metal saltsolutions, in some specific examples, where the alkyl group is a loweralkyl.

Referring to FIG. 1, there is provided a schematic representation of anelectrolytic cell 2 that can be used in the processes for producingalkali alcoholates described herein. In one such embodiment, the cell isused to make sodium methylate. The cell 2 comprises a container or shell3, which is preferably corrosion resistant, a catholyte chamber 6, ananolyte chamber 4, an anode 5, a cathode 7, and an ion-conductingceramic solid electrolyte or ceramic membrane 8, which may be positionedin a scaffold or holder 9. The container 3, and other parts of the cell2, may be made of any suitable material, including metal, glass,plastics, composite, ceramic, other materials, or combinations of theforegoing. The material that forms any portion of the cell 2 ispreferably not reactive with or substantially degraded by the chemicalsand conditions that it is exposed to as part of the process.

The cell 2 further comprises an anolyte inlet 10 for introducingchemicals into the 4, an anolyte, outlet 16 for removing anolytesolution from the anolyte chamber 4, a catholyte inlet 12 forintroducing chemicals into the catholyte chamber 6, and a catholyteoutlet 14 for removing catholyte solution from the catholyte chamber 6.Because gases may be evolved from the cell during operation, ventingmeans (18, 20) are provided to vent, treat and/or collect gases from theanolyte chamber 4 and/or catholyte chamber 6. The means may be a simpleventing system such as openings, pores or holes in the upper portion ofthe container 3, and/or a collection tube, hose, or conduit in fluidcommunication with an airspace or gap above the fluid level in theanolyte and/or catholyte chambers. The gases which are evolved may becollected, vented to outside the cell, sent through a scrubber or othertreatment, or treated in any other suitable manner.

The electrode materials are preferably good electrical conductors andshould be stable in the media to which they are exposed. Any suitablematerial may be used, and the material may be solid or plated, orperforated or expanded. One suitable electrode material is adimensionally stable anode (DSA) which is comprised of ruthenium oxidecoated titanium (RuO₂/Ti). Good anodes can also be formed from nickel,cobalt, nickel tungstate, nickel titanate, platinum and other nobleanode metals, as solids plated on a substrate, such as platinum-platedtitanium. Stainless steel, lead, graphite, tungsten carbide and titaniumdiboride are also useful anode materials. Good cathodes can be formedfrom metals such as nickel, cobalt, platinum, silver and the like andalloys such as titanium carbide with small amounts (preferably only upto about 3%) of nickel, FeAl₃, NiAl₃, stainless steel, perovskiteceramics, and the like. Graphite is also a good cathode material. In apreferred embodiment, the electrodes are chosen to maximize costefficiency effectiveness, by balancing electrical efficiency with lowcost of electrodes.

In one embodiment, the cell may be operated in a continuous mode. In acontinuous mode, the cell is initially filled with anolyte and catholytesolutions and then, during operation, additional solutions are fed intothe cell through the inlets 10, 12 and products, by-products, and/ordiluted solutions are removed from the cell through the outlets 14, 16and/or the venting means 18, 20 without ceasing operation of the cell.The feeding of the reactants anolyte and catholyte solutions may be donecontinuously or it may be done intermittently, meaning that the flow ofa given solution is initiated or stopped according to the need for thesolution and/or to maintain desired concentrations of solutions in thecell, without emptying one or both compartments. Similarly, the removalof solutions from the anolyte compartment and the catholyte compartmentmay also be continuous or intermittent. Control of the addition and/orremoval of solutions from the cell may be done by any suitable means.Such means include manual operation, such as by one or more humanoperators, and automated operation, such as by using sensors, electronicvalves, laboratory robots, etc. operating under computer or analogcontrol. In automated operation, a valve or stopcock may be opened orclosed according to a signal received from a computer or electroniccontroller on the basis of a timer, the output of a sensor, or othermeans. Examples of automated systems are well known in the art. Somecombination of manual and automated operation may also be used.Alternatively, the amount of each solution that is to be added orremoved per unit time to maintain a steady state may be experimentallydetermined for a given cell, and the flow of solutions into and out ofthe system set accordingly to achieve the steady state flow conditions.

In another embodiment, the system is operated in batch mode. In batchmode, the anolyte and catholyte solutions are fed into the cell and thecell is operated until the desired concentration of product is producedat the catholyte. The cell is then emptied, the product collected, andthe cell refilled to start the process again. Alternatively,combinations of continuous mode and batch mode production may be used.Also, in either mode, the feeding of solutions may be done using apre-prepared solution or using components that form the solution insitu.

Flow rate refers to the recycle anolyte and catholyte solutions and notto the in-coming or out-going solutions. It should be noted that bothcontinuous and batch mode have dynamic flow of solutions. In continuousmode, the anolyte make up solution is added so the sodium concentrationis maintained at a certain concentration. In a batch mode, a certainquantity of sodium salt is used and sodium loss in the anolyte due toits transfer through the membrane to the catholyte in not replenished.The operation is stopped when the sodium ion concentration in theanolyte reduces to a certain amount or when the appropriate sodiummethylate concentration is reached in the catholyte.

In some specific embodiments, it is preferred that only electrolyticreactions occur in the cell and that galvanic reactions be eliminatedor, at least, greatly minimized. Preferred ion conducting membranesinclude those which eliminate or minimize galvanic reactions and promoteonly electrolytic reactions and have one or more of the followingcharacteristics: (1) high ionic conductivity with minimum, preferablynegligible, electronic conductivity; (2) high selectivity to preferredionic species; (3) physical separation (dense ceramic electrolyte) ofthe anolyte from the catholyte

The membrane 8 selectively transports a particular, desired cationspecies from the anolyte to the catholyte side even in the presence ofother cation species. The membrane is also significantly or essentiallyimpermeable to water and/or other undesired metal cations. In somespecific embodiments, the membrane has a current density from about 0.5to about 1 amp/in², including about 0.6, 0.7, 0.8, and 0.9 amp/in².

In accordance with the present invention, ceramic NaSICON (Sodium SuperIonic Conductors) materials are utilized for their characteristics ofhigh ion-conductivity for alkali metal ions at low temperatures,selectivity for alkali metal ions, current efficiency and chemicalstability in water, ionic solvents, and corrosive alkali media understatic and electrochemical conditions. Such membranes may have one ormore, or all, of the following desirable characteristics which make themsuitable for aqueous and non-aqueous electrochemical applications. Onecharacteristic is that, being dense, the membrane is at leastsubstantially impervious to water transport, and is not influenced byscaling or precipitation of divalent ions, trivalent ions, andtetravalent ions or dissolved solids present in the solutions. Anotherbeneficial characteristic of the membrane is that it may selectivelytransport sodium ions in the presence of other ions at a transferefficiency that is in some instances above 95%. Yet anothercharacteristic is that the membrane provides the added benefits ofresistance to fouling by precipitants, and/or electro-osmotic transportof water, which is common with organic or polymer membranes. Suitablemembranes may also or instead have other characteristics mentionedelsewhere herein.

Preferred ceramic membranes are essentially impermeable to at least thesolvent components of both the catholyte and anolyte solution. Oneadvantage of these ion-conducting solid electrolyte or ceramic membranesis their low or even negligible electronic conductivity, which virtuallyeliminates any galvanic reactions from occurring when an appliedpotential or current is removed from the cell containing the membrane.Ceramic membranes comprising NaSICON materials typically are veryselective to a specific ion and hence have a high transference number ofpreferred species, implying very low efficiency loss due to near zeroelectro-osmotic transport of water molecules. Polymeric membranesgenerally have low transference number of preferred species and, havelow transfer efficiency.

As noted above, in a specific embodiment, the cation conducted by themembrane is the sodium ion (Na⁺). Preferred sodium ion conductingceramic membranes include NaSICON membrane compositions comprisingNaSICON materials and membrane types in U.S. Pat. No. 5,580,430, herebyincorporated by reference in its entirety. Other analogs of NaSICON totransport ions such as Li and K, to produce other alkali alcoholates areknown to those of ordinary skill in the art, and their use isencompassed within the scope of this invention. These ion conductingmembranes comprising NaSICON materials are particularly useful inelectrolytic systems for simultaneous production of alkali alcoholates,by electrolysis of an alkali (e.g., sodium) salt solutions. In specificmethods, a solid sodium ion conducting ceramic membrane separates twocompartments of a cell. The sodium ions transfer across the membranefrom the anolyte to the catholyte chamber under the influence ofelectrical potential to generate sodium alcoholates. Preferred ionspecific membranes do not allow transport of water therethrough, whichis useful in making the water sensitive alkali alcoholates. Furthermore,these membranes have low electronic conductivity, superior corrosionresistance, and high flux of specific alkali ions providing high ionicconductivity.

While the ceramic materials disclosed herein encompass or include manyformulations of NaSICON materials, this disclosure concentrates on anexamination of NaSICON-type materials for the sake of simplicity. Thefocused discussion of NaSICON-type materials as one example of materialsis not, however, intended to limit the scope of the invention. Forexample, the materials disclosed herein as being highly conductive andhaving high selectivity include those super ion conducting materialsthat are capable of transporting or conducting any alkali cation, suchas sodium (Na), lithium (Li), potassium (K), ions for producing alkalialcoholates.

Ceramic membranes comprising NaSICON materials may be formed by ceramicprocessing methods such as those known in the art. Such membranes may bein the form of very thin sheets supported on porous ceramic substrates,or in the form of thicker sheets (plates) or tubes. A cell employingNaSICON flat circular disc is illustrated in FIG. 2. where concentratedsodium methylate is formed in the catholyte chamber.

The ceramic materials disclosed herein are particularly suitable for usein the electrolysis of alkali metal salt solutions because they havehigh ion-conductivity for alkali metal cations at low temperatures, highselectivity for alkali metal cations, good current efficiency andstability in water and corrosive media under static and electrochemicalconditions. Comparatively, beta alumina is a ceramic material with highion conductivity at temperatures above 300° C. but has low conductivityat temperatures below 1000° C., making it less practical forapplications below 100° C.

Preferred ceramic-based alkali metal cation conducting membranes mayinclude one or more of the following features and use characteristics:solid; high alkali ion conductivity at temperatures below 100° C.; highselectivity for particular alkali cations (e.g. Na⁺); sodium transferefficiency greater than 90%; stability in organic or inorganic sodiumsalts and chemicals; density greater than 95% of theoretical; generallyimpervious to H₂O transport; electronically insulating; and resistant toacid, alkaline, caustic and/or corrosive chemicals.

Na-ionic conductivity in NaSICON structure has an Arrhenius dependencyon temperature, generally increases as a function of temperature. Thesodium ion conductivity of NaSICON ranges from 3×10⁻² S/cm to 8×10⁻²S/cm from room temperature to 85° C.

NaSICON-type materials, especially of the type described herein, havelow or negligible electronic conductivity, and as such aid in virtuallyeliminating the occurrence of any galvanic reactions when the appliedpotential or current is removed. Preferred NaSICON analogs have verymobile cations, including, but not limited to lithium, sodium, andpotassium ions, that provide high ionic conductivity, low electronicconductivity and comparatively high corrosion resistance.

The cation conductive ceramic materials referred herein for use inelectrolytic cells can be used successfully in the formation of alkalialcoholates from the electrolysis of aqueous sodium salt solutions,including, but not limited to, such solutions as sodium carbonate,sodium nitrate, sodium phosphate, sodium hypochlorite, sodium chloride,sodium perchlorate, and sodium organic salts.

An ideal solid electrolyte is an electronic insulator and an excellentionic conductor. The NaM₂(BO₄)₃ is the best known member of a largefamily of sodium conducting compounds and crystalline solutions thathave been extensively studied. The structure has hexagonal arrangementand remains stable through a wide variation in atomic parameters as wellin the number of extra occupancies or vacancies.

Preferred ceramic membranes include the ceramic membranes comprisingNaSICON materials include those having the formula NaM₂(BO₄)₃ and thosehaving the formula M¹M²A(BO₄)₃, but also including compositions ofstoichiometric substitutions where M¹ and M² are independently chosen toform alkali analogs of NaSICON. Substitution at different structuralsites in the above formula at M, M¹, M², A, and B may be filled by the2+, 3+, 4+, 5+ valence elements. Other suitable alkali ion conductorceramic materials have the formula: M_(1+X)A_(2−x) N_(y)B_(x)C_(3−x)O₁₂(0<x<2) (0<y<2), where M¹M²=Li, Na, K, and non-stiochiometriccompositions, in the above formulation with substitution at differentstructural sites in the above formula M¹, M², A, N, B and C by the 2+,3+, 4+, 5+valence elements.

The processing of Na₃Zr₂Si₂PO₁₂ and Na₅RESi₄O₁₂ type NaSICONcompositions (where RE is either Yttrium or a rare earth element)proceed as follows. Membranes are systematically synthesized bysolid-state oxide mixing techniques. A mixture of the startingprecursors is mixed in methanol in polyethylene jars. The mixedprecursor oxides are dried at 60° C. to evolve the solvent. The driedpowder or material is calcined at 800° C., to form the requiredcomposition. The calcined material is wet ball milled with zirconiumoxide media (or other metal media) to achieve the prerequisite particlesize distribution. Green membranes at 0.60 to 2.5 inch diameter sizesare pressed by compaction in a die and punch assembly and then sinteredin air at temperatures between 1100° C. and 1200° C. to make denseceramic oxides. XRD analysis of NaSICON composition is performed toidentify the crystal structure and phase purity. Stoichiometric andnon-stoichiometric compositions of the Na₃Zr₂Si₂PO₁₂ type formula areone type of ceramic produced in this manner. Non-stoichiometric in thisinstance means un-equivalent substitution of Zr, Si, and/or P in theformula. As such, specific formulations may include Ti, Sn, and Hfpartial substitution at the Zr site. In several example compositionsthere is partial substitution of Ti, Sn, and Ge at the Zr, Si, and Psites. Examples of compositions and processing for NaSICON include thefollowing: S. Balagopal, T. Landro, S. Zecevic, D. Sutija, S. Elangovan,and A. Khandkar, “Selective sodium removal from aqueous waste streamswith NaSICON ceramics”, Separation and Purification Technology 15 (1999)231-237; Davor Sutija, Shekar Balagopal, Thom Landro, John Gordon,“Ceramic Cleansers, Environmental applications of Sodium Super-IonicConducting Ceramics”, The Electrochemical Soc. Interface. 5 (4) (1996)26; R. D. Shannon, B. E. Taylor, T. E. Gier, H. Y. Chen, T. Berzins,Ionic Conductivity in Na₅YSi₄O₁₂ type silicates, Inorg. Chem. 17 (4)(1978) 958.; S. H. Balagopal, J. H. Gordon, A. V. Virkar, A. V. Joshi,U.S. Pat. No. 5,580,430, 1996; and J. B. Goodenough, H. Y. P. Hong, J.A. Kafalas, Fast Na+ ion transport in skeleton structures, Mater. Res.Bull. 11 (1976) 203.

The stability or resistance to corrosive media of the preferred membranematerials described herein may be enhanced by chemistry variation.NaSICON-type formulations which have one or more of the preferredcharacteristics described herein are suitable for use in the presentinvention.

The membrane may have flat plate geometry, tubular geometry, orsupported geometry. The solid membrane is preferably sandwiched betweentwo pockets, preferably made of a chemically-resistant HDPE plastic andsealed, preferably by compression loading using a suitable gasket oro-ring, such as an EPDM o-ring.

The phrase “significantly impermeable to water”, as used herein, meansthat a small amount of water may pass through the membrane, but that theamount that passes through is not of a quantity to diminish theusefulness of the sodium methylate solution product. The phrase“essentially impermeable to water”, as used herein, means that no waterpasses through or that if water passes through the membrane, its passageis so limited so as to be undetectable by conventional means. The words“significantly” and “essentially” are used similarly as intensifiers inother places within this specification.

The NaSICON type materials or modified NaSICON materials referred hereinare useful, for example, as sodium-ion conducting membranes inelectrolytic cells. For the production of sodium methylate, as anexample, an aqueous solution of sodium hydroxide, is charged into theanolyte chamber. A dilute solution of sodium methoxide in methanol orpure methanol is charged into the catholyte chamber. It is desirable tostart with conductive electrolyte to keep the operating voltage of cellas low as practical.

An example of an overall electrolytic reaction, using sodium hydroxideas the source of sodium ion, is as follows:Anode: 2OH⁻→½O₂+H₂O+2e⁻Cathode: 2CH₃OH+2e⁻+2Na⁺−2NaCH₃O+H₂Overall: 2CH₃OH+2NaOH→2NaOCH₃+H₂+½O₂+H₂O

These reactions are electrolytic reactions (FIG. 2), taking place underan induced current wherein electrons are introduced or are removed tocause the reactions. The reactions proceed only so long as a current isflowing through the cell. Contrary to electrolytic reactions, galvanicreactions may occur when an applied potential to the cell is removed,which tends to reduce the efficiency of the electrolytic cell. It ispreferred that only electrolytic reactions occur in the cell and thatgalvanic reactions be eliminated or, at least, greatly minimized.

The anolyte solution which is the source of the sodium cation or otheralkali metal cation in the process may be a neutral salt, such as sodiumchloride, or it may be a caustic solution such as sodium hydroxide.Solutions or by-products of industrial processes may be used as a sodiumsource. In a preferred embodiment, aqueous sodium hydroxide is used.Sodium hydroxide is a preferred solution because it is inexpensive andits use produces water and oxygen gas at the anode. Accordingly,although the discussion which follows is based on use of sodiumhydroxide, it can be adapted to other alkali chemicals, with theunderstanding that the reaction gas products at the anode will differdepending on the chemistry of the salt used in anolyte.

The sodium hydroxide (caustic) is fed into the anolyte compartment 4through inlet 10. The sodium hydroxide solution may be of any grade orpurity. The purity of sodium hydroxide solution is not critical becausethe ceramic membrane comprising NaSICON materials is selective totransport of sodium ions unlike organic membranes. Similarly, methanolis fed into the catholyte compartment 6 of the cell 2 through the inlet12. The methanol is preferably free of moisture as its presence willlead to the formation of sodium methylate of low quality. In oneembodiment, the catholyte compartment and/or the anolyte compartment ispurged with one or more inert or nonflammable gases such as nitrogen andargon.

In some embodiments, for sodium methylate production, the cell may beoperated at temperatures from about 20° C. to about 80° C., includingabout 25° C., 30° C., 40° C., 50° C., 60° C., and 70° C., and ranges oftemperatures bounded by these enumerated temperatures. Preferably, thetemperature is maintained below the boiling point of the solutions usedas catholyte. The cell is preferably operated at ambient pressure, withthe pressure in the two compartments being substantially equal.

Under the influence of the electric potential, the sodium ions aretransported from the anolyte side across the membrane to the catholyteside where the sodium ions react with methanol to form sodium methylate,while hydroxyl ions are oxidized at the anode to produce oxygen. In somesuch embodiments, the concentration of sodium cation in the anolytecompartment 4 is maintained in a desired range by a combination offeeding additional sodium hydroxide 10 into the anolyte compartment andremoving dilute or diluted caustic solution 16 from the anolytecompartment.

As the reactions progress, the concentration of sodium methylate in thecatholyte compartment 6 begins to increase. Once the concentrationreaches a desired level, sodium methylate solution product is preferablyremoved from the catholyte compartment through outlet 14, and its volumereplaced by methanol through inlet 12. The concentration of sodiummethylate in the catholyte outlet stream 14 may be monitored by anysuitable means, including, but not limited to, specific gravity, sodiumconcentration, and other methods known in the art.

In embodiments of the electrochemical cell, the catholyte comprises oneor more alkali alcoholates, and the anolyte comprises one or moreaqueous inorganic and/or organic salts. Preferred sodium salts in theanolyte include sodium hydroxide, sodium chloride, sodium carbonate,sodium bicarbonate, sodium sulfate, sodium chlorate, sodium chloride,sodium nitrate, sodium phosphate, sodium perchlorate, sodium nitrite andother sodium based sodium salts, and combinations of two or more suchsalts. Salts of other alkali metals such as potassium, and lithium, andwith these same anions, and other suitable anions, as well ascombinations of salts having different anions, different cations orboth, are also contemplated, including where sodium is not the metalcation being conducted by the electrolyte.

As discussed above, the electrochemical cell may be operated batch wiseor continuously. Continuous operation in connection with the embodimentof FIG. 2 involves continuous introduction of methanol or lowconcentration of sodium methoxide in methanol to the catholyte andremoval of desired concentration of sodium methoxide solution from thecatholyte. This is paired with addition of NaOH (and/or another sodiumsalt) to the anolyte so that the concentration of the caustic ispreferably substantially balanced with the concurrent transport ofsodium ions across the membrane.

Batch wise operation involves charging the cell with a feed saltsolution as the anolyte, dilute sodium methoxide solution in methanol,or methanol as the catholyte and operating the cell at the desiredtemperature and voltage until a sodium methoxide in methanol solutionhaving a desired concentration is obtained. Cells of the presentinvention employing ceramic membranes comprising NaSICON materials maybe operated using relatively pure anolyte solutions, or by usingrelatively impure anolyte solutions such as by-products and contaminatedimpure caustic from industrial chemical processes. In one embodiment,caustic solutions of 50% by weight NaOH concentration are used.

The methods of the present invention, including those described above,are clean in that essentially all materials made from the process areuseful, recyclable, and/or not environmentally harmful. For example, thedilute caustic solution 16 discharged from the anolyte compartment 4 maybe concentrated and then used again, including being recycled back intothis process. The oxygen 18 and hydrogen 20 gases produced at theanolyte compartment and the catholyte compartment, respectively, may becollected, transported, and/or pressurized for use. The gas may also berun through a condenser or a scrubber to remove impurities. The hydrogengas produced can be used as a fuel or in an alternative energy sourcesuch as fuel cells. In one embodiment, the hydrogen gas produced by thecell is used, directly or indirectly, to power the cell and/or itscomponents. Alternatively, the gaseous output may be vented to theenvironment, with or without the use of scrubbers, fire suppressors, orother safety precautions.

Methods using sodium hydroxide as a starting solution may also begenerally cost effective as compared to other methods where sodium metalis reacted directly with methanol to form sodium methylate. Sodiumhydroxide is easier and safer to handle than sodium metal, whichrequires special storage, handling, and delivery systems to preventauto-ignition of sodium metal or its violent exothermic reaction withwater in the environment. Sodium hydroxide is generally also lessexpensive than sodium metal for an equivalent molar quantity of sodiumatoms.

In view of the foregoing general principles and considerations, specificmethods for producing sodium methylate solution may be carried out. Onepreferred method comprises feeding methanol into a catholyte compartmentof an electrolytic cell, feeding sodium hydroxide or othersodium-containing caustic solution into the anolyte compartment of thecell, and applying an electric potential to the cell, wherein theanolyte and catholyte compartments are separated by a ceramic membranethat selectively transports sodium ions and is substantially impermeableto water. The cell may operate in continuous mode, in batch mode, orsome combination of the two. The ceramic membrane preferably has one ormore of the preferred properties set forth herein above.

In a preferred embodiment where sodium methylate in methanol is made,the sodium methylate solution produced preferably comprises about 1% toabout 32% by weight sodium methylate in methanol, preferably about 20%to about 32% or about 25% to about 28% by weight, including those having23%, 24%, 26%, 27%, 29%, 30%, and 31% sodium methylate by weight.Solutions having sodium methylate concentrations above and below theselimits are also presently.contemplated, keeping in mind thatconcentrations significantly above 33% may not be desirable as thesaturation point of the sodium methylate in methanol solution isreached. The sodium methylate produced preferably has a high purity,with the purity being primarily limited by the purity of methanol thatis used as a starting material. Preferred sodium methylate solutions arealso substantially free of mercury and/or other heavy metals. As usedherein, “substantially free” of mercury is a broad functional term thatincludes where there is essentially no mercury detectable within testlimits (“essentially free”) and where there is a small amount of mercurydetected, but not at a quantity to limit the material's use in biodieselproduction. In one embodiment, the amount of mercury in the solution isnot detectable by methods of detection used in the art. In a preferredembodiment, the sodium methylate solution is colorless or substantiallycolorless.

Some preferred embodiments are illustrated by the examples which follow.These examples are intended for illustration only, and are not intendedto be limiting.

EXAMPLE 1

Ceramic membranes comprising NaSICON materials were evaluated in singlemembrane cells, to synthesize sodium methoxide from caustic andmethanol. An individual, 900 microns thick single membrane (14.27 cm²area) was assembled in a two compartment open cell with platinumelectrodes. The cells were operated at a temperature of 24° C. atconstant current density of 100 mA/cm². The voltage (IR) drop across themembrane was measured with lugging capillaries set up. The concentrationof the starting catholyte solution was 9.5 wt % sodium methoxide inmethanol. The solution was prepared by mixing crystals of sodiummethoxide from vendor with methanol. The resulting starting solutionswere slightly yellowish in color.

The performance of two independent cells is graphically shown in FIG. 3.One membrane has a lower voltage drop across the membrane compared tothe other membrane at similar operating conditions. The voltage drop ofthe first membrane averaged around 0.7 volts as compared to 1 volt forthe second membrane.

EXAMPLE 2

An experiment was performed to determine the ionic resistance of sodiummethoxide as a function of operating parameters such as concentration,temperature, and electrode distance. An open cell was assembled with nomembrane between the electrodes. An electrode spacing apparatus was usedto adjust the distance between electrodes. Sodium methoxide solutions at20, 25, and 30 wt % grades were prepared and their resistances weremeasured at three different temperatures (25, 30, and 40° C.) using theA.C. impendence spectrometry.

The results are shown in FIG. 4. The biggest contributor to the overallresistance of the cell is the sodium methylate solution. The solutionresistance ranges from 5 to 70 ohms depending on the operatingparameters. The tests show that the electrical conductivity of thesodium methylate solution is function of concentration and temperatureof the solution.

EXAMPLE 3

An experiment was conducted to evaluate the effect of flow rates ofanolyte and catholyte, and electrode distance from the membrane on cellperformance. This test was conducted in a standup closedlaboratory-scale cell, such as the commercial Electro Cell MP (ChematurEngineering AB, Karlskoga, Sweden). The electrodes were initially placedat approximately 0.5 cm away from the membrane on either side. Using aperistaltic pump, the initial flow rate was set at 2.5 setting on thepump speed controller and the cell was operated until steady voltage wasachieved. The flow rate was then increased to the 7.5 setting on thespeed controller.

The results and other details of the experiment are shown in FIG. 5. Thetotal voltage of the cell drops as the flow rate of the solutionincreases due to better dissipation of gases evolved at the electrodes,contributing positively to the overall cell operation and theconductivity of solutions.

EXAMPLE 4

Two-inch diameter circular ceramic membranes comprising NaSICONmaterials with a total active area of 34.63 cm² were housed in ahigh-density polyethylene (HDPE) scaffold and retrofitted into atwo-compartment electrochemical cell. DSA electrodes were used in thecell for this test. The flow rates of the anolyte and catholytesolutions in this test were maintained at 1.6 gal/min. The testingparameters and the results are listed in Table I. The performance of thecell is presented in FIG. 6.

The anolyte was a 16 wt % NaOH solution and the catholyte was 22.63weight % sodium methoxide solution. The cell was operated ingalvanostatic mode at 100 mA/cm² current density in a circulating batchmode. This test was performed at a temperature of 30° C. FIG. 6represents the performance of one membrane based cell to produce sodiummethoxide. The gradual increase in cell voltage after 16 hours ofperformance is attributed to changes in concentration of the caustic inthe anolyte and sodium methoxide in the catholyte. The voltage heldsteady during the first 8 hours of continuous operation. The flow ratesof anolyte and catholyte solutions were maintained at 1.6 gal/min. Theoperating conditions and test results are listed in Table I below.Sodium methylate was made in the catholyte side of the cell. Theobjective of this test to produce sodium methylate from caustic andmethanol was successfully met. A 4.28 wt % increase in concentration ofsodium methylate in the catholyte was measured after the test. TABLE 1Test parameters and results Test 42604 Parameters: Total Amp hrs 55.47Amps 3.46 Total kWhrs 0.861 Anode DSA Anode % CE 96.27% Cathode NiKW.hr/lb_(NaOCH3) 3.63 NASG NaOCH3 gain in Cath (g) 107.65 Membrane11204 Area (cm²) 34.63 Thickness (mm) 1.3 Mass Balance: 0 Hrs VolumeTotal M (mole/ Start (ml) S.G. wt (g) wt % Liter

) Anolyte 3869 1.163 4500 15.99 4.465 Catholyte 3822 0.919 3513 22.633.85 Totals 7691.61 8013 16.033 Hrs Volume Total Theoretical Na* ActualNa* M (mole/ End (ml) S.G. wt (g) wt % change (g) change (g) Liter

) Anolyte 3869 1.1 4256.2 14.36 47.585 45.812 4.465 Catholyte 3507 0.8863107 26.91 3.85 Totals 7376 7364 Recovery: 92%*Material balance does not include solution loss due to evaporation.

EXAMPLE 5

The ceramic membranes comprising NaSICON materials and cell set up usedin Example 4 were used to perform in this test. The anolyte was operatedin a continuous mode, and catholyte in a batch mode. This test wasperformed to evaluate the cell performance at different operatingcurrent densities. The effect of temperature and sodium current densityon the performance of membranes was measured. The operating conditionsand results of this test are reported in Table II.

Initially the cell was operated at a current density of 100 mA/cm² for30 minutes, then the current was increased to 200 mA/cm² until 2.5hours, when the current was finally increased to approx 300 mA/cm². Asthe current was increased at each step in this test, the temperaturelikewise increased due to heat transfer and exothermic reaction in thecatholyte. The membranes performed consistently at the high currentdensity (300 mA/cm²) as shown in the FIG. 7. TABLE II Test parametersand results Current Density 1. TEST 42904 Anolyte Catholyte mA/cm²mA/in² Initial 4.465 2.92 Concentration (M) Final NA 3.34 Concentration(M) Initial wt % 16 18.15 Final wt % NA 20.07 Temperature (° C.) 54 48100 645.16 58 51 200 1290.32 48 62 296 1909.67 Surface Area (cm²) 34.63Surface Area (in²) 5.37 Test Duration (hrs) 4.07

EXAMPLE 6

This test was performed with the ceramic membranes comprising NaSICONmaterial in a prototype cell (Electro Cell MP) to produce highconcentration sodium methylate from sodium hydroxide and methanol. FourNaSICON membranes (1.5 inch diameter and 1.3 mm thickness) were housedin a HDPE scaffolds and retrofitted into an Electro Cell MP. This testwas conducted with the anolyte held at a temperature of 50° C. and thecatholyte at a temperature of 25° C.

Heating the anolyte to a temperature of 50° C. caused the catholyte toheat up as well due to heat transfer across the scaffold. A lowoperating cell voltage was observed in this test (FIG. 8). As the testcontinued, the catholyte heated up quickly and eventually exceeded theanolyte's temperature, indicating an exothermic reactions taking placein the catholyte chamber of the cell.

This test was carried out for four hours to prove the demonstration witha prototype cell to make sodium methoxide.

EXAMPLE 7

This test was conducted to produce sodium methylate by purging thecatholyte holding tank with nitrogen gas as a blanket.

A single ceramic membrane comprising NaSICON material was assembled inan open cell, which was operated at room temperature with nitrogen gasbubbling through the sodium methoxide solution in the catholyte chamber.The open cell had two small openings at the top of each compartment ofthe cell to insert lugging capillaries. The lugging capillariesspecifically allow continuous monitoring of the IR drop (voltage) acrossthe membrane during steady state operation of a cell. The platinumelectrodes in this laboratory scale design were spaced about 6 cm oneither side of the membrane. Starting sodium methoxide solution wasprepared from a 30 wt % solution of methoxide, supplied by vendor(ACROS), and diluted with anhydrous methanol to a 10 wt % solution.

In this test, the concentration of sodium methylate increased from a 10wt % solution to 28.3 wt %, (FIG. 9). The cell was operated for a totalof 16 hours. The final product had a tint of light yellow. Thediscoloration of the sodium methoxide was found to be due to thereaction of sodium methoxide with the tubing material and not from thelack of nitrogen blanket, which is useful to keep the sodium methoxidefrom reacting with atmospheric moisture, forming caustic andconsequently causing sodium methylate contamination.

EXAMPLE 8

A larger scaffold was designed and manufactured at Ceramatec, to housefour 2-inch diameter ceramic membranes comprising NaSICON material toprovide an active area of 60 cm². This cell was used to demonstratecontinuous and batch mode operations and to complete one specific testlasting over 43 hours to optimize the electrochemical factors as afunction of starting concentration of sodium methylate in the catholyte.

One test was performed under nitrogen blanket to prevent sodiummethoxide from reacting with the atmospheric moisture to form causticand to prevent chemistry changes.

A summary of the results from several batch tests is provided in TableIII below. Test number 7, provides interesting and useful information.It shows that operating the cell in a batch mode can be more beneficial,in terms of power consumption, than operating it in a continuous mode,which would require maintaining sodium methylate concentration in thecatholyte between 25 to 28% range at all the times during the operation.

The sodium transfer efficiency of the anolyte and catholyte in all thetests was above 90%.

The ceramic membranes showed no signs of degradation based on x-raydiffraction and scanning electron microscope analysis or loss of steadystate performance. TABLE III Summary of tests results Batch StartingFinal Duration Starting Ending Cell mode NaOCH₃ NaOCH₃ of test cell cellOperation Temp N₂ tests wt % wt % (hrs) voltage voltage mode (° C.) flow1 23.83 26.65 10.6 14.5 16.3 Batch 50 No 2 20.34 23.7 11.7 11.4 13.3Batch 50 No 3 23.7 20.91 11.6 14 16.7 Batch 50 No 4 26.91 29.44 9.6 12.522.5 Batch 50 No 5 20.34 27.07 21.7 12.3 17.2 (A) Cont. 50 No 6 11.3522.33 19.77 8.6 12.8 Batch 50 No 7 5.41 29.5 43.22 9.1 17.5 (A) Cont. 50Yes

The concentration of sodium methoxide produced in a 60cm² active areaceramic membrane comprising NaSICON material cell (Electro-Cell MP) as afunction of operating voltage is shown in FIG. 10. The graph shows thecalibration curve for estimated voltages required to achieve desiredconcentration of sodium methoxide in the catholyte compartment of theceramic membrane comprising NaSICON material based electrochemical celloperating at 100 mA/cm² current density, and at approximately 50° C.temperature.

EXAMPLE 9

The process to make sodium methylate will work equally efficiently whenan impure caustic from azide plant or other sodium based industrial orcontaminated aqueous salts are used as the starting anolyte precursor,with nickel or stainless steel electrodes. Several tests were carriedout using impure caustic and nickel electrodes.

The results from the tests are given below in Tables IV, V and VI. Testswere conducted with pure caustic (Table IV), impure caustic with 1.4%azide (Table V), and impure caustic with 7.5% azide (Table VI). FIGS.11, 12 and 13 show cell performance to produce sodium methylate frompure and impure sodium hydroxide solutions as anolyte.

The results show that the process using ceramic membranes comprisingNaSICON materials provides similar sodium transfer current efficiencywith clean or impure caustic. TABLE IV Results of the tests conductedwith clean caustic Parameters: Results: Amps 7.0 Cath % CE 107.10% AnodeNi kWhr/lb NaOCH₃ 2.95 Cathode Ni Area (cm²) 60 Thickness (mm) 1.3 MassBalance: 0.00 hrs Volume Total Start (ml) S.G. wt (g) wt % Anolyte4025.00 1.280 5152.00 24.79 Catholyte 4300.00 0.827 3556.10 6.72 totals:8325.00 8708.10 47.00 hrs Volume Total Theoretical Na* Actual Na* End(ml) S.G. wt (g) wt % change (g) change (g) Anolyte 3925.00 1.1724600.10 16.09 282.35 308.83 Catholyte 4000.00 0.945 3778.28 25.12 282.35302.40 totals: 7925.00 8378.38 Recovery: 96.21% Data: Anolyte Catholytetime temp temp sample (hrs) Volts Amphrs KWhrs ° C. ° C. 1 0 11.7 0.000.00 49.2 26.7 2 47.00 14.0 329.00 4.61 48.3 56.9*Not counting the amount recovered in the condenser

TABLE V Results of the tests conducted with impure caustic Parameters:Amps 7.0 Anode Ni Cathode Ni Area (cm²) 60   Thickness (mm) 1.3 Results:Cath % CE 100.81% Assay of starting Anolyte Al 15 mg/L Ba 6 mg/L Ca 1mg/L Fe 2 mg/L K 965 mg/L Mo 23 mg/L Zn 1 mg/L Cl 2593 ppm NO₃ 248 ppmNaN₃ 14348 ppm SO₄ 287 ppm Mass Balance: 0.00 hrs Start Volume (ml) S.G.Total wt (g) wt % NaN₃ (g) Anolyte 4275.00 1.216 5198.40 20.45 75Catholyte 4250.00 0.816 3467.58  6.50 totals: 8525.00 8665.98 50.00 hrsActual Theoreti- Na⁺ Volume Total NaN₃ cal Na⁺ change End (ml) S.G. wt(g) wt % (g) change (g) (g) Anolyte 4225.00 1.108 4680.88 11.14 67300.37 311.60 Catholyte 3800.00 0.936 3555.28 26.33 300.37 302.82 total:8025.00 8236.16 Recovery: 95.04% Data: Anolyte Catholyte sample time(hrs) Volts Amphrs KWhrs temp ° C. temp ° C. 1 0 11.7 0.00 0.00 45.128.6 2 50.00 16.4 350.00 5.74 49.7 60.0*-Not counting the amount recovered in the condenser

TABLE VI Results of the tests conducted with impure caustic Assay ofstarting Anolyte Parameters: Amps 7.0 Al 17 mg/L Anode Ni Ba 6 mg/LCathode Ni Ca 2 mg/L Area (cm²) 60 Fe 2 mg/L Thickness (mm) 1.3 K 1413mg/L Results: Mo 23 mg/L Cath % CE 107.69% Zn 1 mg/L Cl 3204 ppm NO₃ 226ppm NaN₃ 74900 ppm SO₄ 549 ppm Mass Balance: 0.00 hrs Volume Total NaN₃Start (ml) S.G. wt (g) wt % (g) Anolyte 4525.00 1.305 5905.13 24.77 442Catholyte 4250.00 0.818 3476.50 6.79 totals: 8775.00 9381.63 47.00 hrsVolume Total NaN₃ Theoretical Na* Actual Na* End (ml) S.G. wt (g) wt %(g) change (g) change (g) Anolyte 4475.00 1.228 5495.30 16.93 417 282.35306.17 Catholyte 3900.00 0.946 3689.40 25.74 282.35 304.07 totals:8375.00 9184.70 recovery: 97.90% Data Anolyte Catholyte time temp tempsample (hrs) Volts Amphrs KWhrs ° C. ° C. 1 0 12.8 0.00 0.00 40.7 27.0 247.00 15.8 329.00 5.20 48.1 57.2*Not counting the amount recovered in the condenser

The various methods and techniques described above provide a number ofways to carry out the invention. Of course, it is to be understood thatnot necessarily all objectives or advantages described may be achievedin accordance with any particular embodiment described herein. Thus, forexample, those skilled in the art will recognize that the methods may beperformed in a manner that achieves or optimizes one advantage or groupof advantages as taught herein without necessarily achieving otherobjectives or advantages as may be taught or suggested herein.

Furthermore, the skilled artisan will recognize the interchangeabilityof various features, materials and conditions. Similarly, the variousfeatures and steps discussed above, as well as other known equivalentsfor each such feature or step, can be mixed and matched by one ofordinary skill in this art to perform methods in accordance withprinciples described herein.

Although the invention has been disclosed in the context of certainembodiments, it will be understood by those skilled in the art that theinvention extends beyond the specifically disclosed embodiments to otheralternative embodiments and/or uses and obvious modifications andequivalents thereof. Accordingly, the invention is not intended to belimited by the specific disclosures of preferred embodiments herein, butinstead that it includes all modifications and alternatives comingwithin the true scope and spirit of the invention as embodied in theattached claims.

1. A method for producing alkali metal alcoholates, the methodcomprising: feeding a catholyte solution comprising an alcoholcorresponding to the alkali metal alcoholate desired to be produced intoa catholyte compartment of an electrolytic cell; feeding an anolytesolution comprising an aqueous solution of one or more alkali metalsalts corresponding to the alkali metal alcoholate desired to beproduced into an anolyte compartment of the cell; and applying anelectric potential to the cell, wherein the anolyte compartment and thecatholyte compartment are separated by a ceramic membrane that, uponapplication of electric potential to the cell, selectively transportsalkali metal cations from the anolyte compartment to the catholytecompartment, and is substantially impermeable to water; and wherein analkali metal alcoholate solution is formed in the catholyte compartmentof the cell.
 2. The method of claim 1, wherein the catholyte solutioncomprises methanol or a solution of sodium methoxide in methanol.
 3. Themethod of claim 1, wherein the anolyte solution comprises an alkalimetal salt selected from the group consisting of: sodium hydroxide,sodium chloride, sodium carbonate, sodium bicarbonate, sodium sulfate,sodium chlorate, sodium nitrate, sodium phosphate, sodium perchlorate,sodium nitrite, sodium nitrate, sodium phosphate, sodium hypochlorite,and sodium organic salts.
 4. The method of claim 1, wherein the anolytesolution comprises an alkali metal salt selected from the groupconsisting of: lithium hydroxide, lithium chloride, lithium carbonate,lithium bicarbonate, lithium sulfate, lithium chlorate, lithium nitrate,lithium phosphate, lithium perchlorate, lithium nitrite, and anycombination thereof.
 5. The method of claim 1, wherein the anolytesolution comprises an alkali metal salt selected from the groupconsisting of: potassium hydroxide, potassium chloride, potassiumcarbonate, potassium bicarbonate, potassium sulfate, potassium chlorate,potassium nitrate, potassium phosphate, potassium perchlorate, potassiumnitrite, and any combination thereof.
 6. The method of claim 1, whereinthe electric potential (IR) drop across the ceramic membrane is lessthan about 1.0 volts.
 7. The method of claim 1, wherein the ceramicmembrane selectively transports an alkali metal cation selected from thegroup consisting of: Na⁺, Li⁺, and K⁺.
 8. The method of claim 1, whereinthe ceramic membrane has a current density of at least about 100 mA/cm².9. The method of claim 1, wherein the catholyte is continuously orintermittently fed into the catholyte compartment.
 10. The method ofclaim 1, wherein the anolyte is continuously or intermittently fed intothe anolyte compartment.
 11. The method of claim 1, wherein the ceramicmembrane comprises a NaSICON material.
 12. The method of claim 1,wherein the ceramic membrane comprises an alkali metal analog of aNaSICON material corresponding to the alkali metal cation to betransported.
 13. The method of claim 1, wherein the ceramic membranecomprises a material having the formula M¹M²A(BO₄)₃ where M¹ and M² areindependently chosen from Na, Li, and K; and A and B are independentlyselected from elements having a valence of 2+, 3+, 4+, or 5+.
 14. Themethod of claim 1 wherein the membrane has a flat plate geometry in theform of thin sheets supported on porous ceramic substrates or thickerplates.
 15. The method of claim 1 wherein the membrane has a tubulargeometry in the form of thin sheets supported on porous ceramicsubstrates or thicker tubes.
 16. The method of claim 1 wherein themembrane is coated with sodium ion conducting oxide materials.
 17. Themethod of claim 1, further comprising the step of purging the catholytecompartment with one or more inert or nonflammable gases duringoperation of the electrolytic cell.
 18. The method of claim 1 whereinthe ceramic membrane comprises a ceramic material having the formulaNaM₂(BO₄)₃ where M and B is selected from elements having a valence of2+, 3+, 4+, or 5+.
 19. The method of claim 1 wherein the ceramicmembrane comprises a ceramic material having the formula Na₃Zr₂Si₂PO₁₂.20. The method of claim 1 wherein the ceramic membrane comprises aceramic material having the formula Na₅RESi₄O₁₂ where RE is Yttrium or arare earth element.